ANTIOCH -- Police are investigating several incidents in which people were injured and vehicles were damaged by objects thrown from a Highway 4 overpass.

In separate incidents Thursday, a 49-year-old Brentwood man and a 53-year-old Discovery Bay woman were driving near the G Street overcrossing on Highway 4 when the objects were thrown at their vehicles.

The unknown object smashed through the man's windshield about 9:45 p.m. Thursday and struck him in the arm. Believing he had been shot, the man drove himself to a hospital, where he was treated and released.

A short time later, a woman reported her windshield was shattered by a thrown object. She was not injured, but her vehicle was badly damaged, police said.

An ambulance was also hit by something thrown from the same overpass on Monday, police said. The ambulance was damaged, but no one was hurt, police said.

Anyone with information regarding these incidents is asked to call Det. Matt Koch at 925-779-6895.

Rick Hurd covers crime. Contact him at 925-945-4780 and follow him at Twitter.com/3rdERH.